Pacemaker systems typically include a controller, a battery, a pulse generator and one or more leads. The pulse generator produces pacing pulses for a heart. The leads deliver the impulses to the heart and sense contractions of the heart. A programming module that is separate from the pacemaker system can be used by the doctor to alter the operation of the pacemaker system after it has been installed in a patient.
Some pacemaker systems operate on demand. In other words, the pacemaker system stands by until a natural rate of the upper and lower heart falls below a predetermined rate. When this situation occurs, the pacemaker system sends out pacing impulses to ensure that the heart contracts and pumps blood.
The battery, controller, and pulse generator may be packaged in a sealed housing. The leads typically extend from the sealed housing and have ends that are connected within chambers of the patient's heart. The leads are also typically employed to carry feedback signals from the heart. Using the feedback signals, the controller is able to monitor the heart's activity and trigger the pulse generator appropriately. The battery may be sealed inside of the housing or another component of the pacemaker system. The housing and/or other component is typically removed and the battery is replaced when the stored energy in the battery falls below a threshold. As can be appreciated, replacing the battery requires a patient to undergo additional surgery.
The leads typically include insulated wires that extend from the pulse generator in the housing through a vein to a heart chamber or chambers. The pacemaker system monitors the heart by sensing electrical signals received by the pulse generator through the leads. The signals that are received provide information relating to contraction of the heart chambers. This information is typically sufficient for the controller to decide when pulses are required.
Pacemaker systems exist for single chamber and dual chamber applications. A single chamber pacemaker system usually employs a single lead to carry signals to and from one chamber of the heart. Typically, the lead is connected to the right atrium or the right ventricle. This type of pacemaker is often selected for patients having an SA (sinoatrial) node that sends out signals too slowly but whose electrical pathway to the lower heart is in good condition.
A dual chamber pacemaker usually includes two leads. One lead is located in the right atrium and another lead is located in the right ventricle. This type of pacemaker system can monitor and deliver impulses to either or both of the heart chambers. The dual chamber pacemaker system is typically selected when the SA node signals are too slow and the electrical pathway is partly or completely blocked.
Adaptive rate pacemakers may also be used. Adaptive rate pacemakers typically include additional sensors that monitor the body's need for blood flow. By monitoring this information, the pacemaker can increase and/or decrease the pace to correct for when the heart's natural rate does not increase sufficiently for an increased level of activity.